1. Field
The present invention relates to an elevator, as discussed below.
2. Description of Related Art
One of the objectives in elevator development work is to achieve an efficient and economical utilization of building space. In recent years, this development work has produced various elevator solutions without machine room, among other things. Good examples of elevators without machine room are disclosed in specifications EP 0 631 967 (A1) and EP 0 631 968. The elevators described in these specifications are fairly efficient in respect of space utilization as they have made it possible to eliminate the space required by the elevator machine room in the building without a need to enlarge the elevator shaft. In the elevators disclosed in these specifications, the machine is compact at least in one direction, but in other directions it may have much larger dimensions than a conventional elevator machine.
In these basically good elevator solutions, the space required by the hoisting machine limits the freedom of choice in elevator lay-out solutions. Some space is needed to provide for the passage of the hoisting ropes. It is difficult to reduce the space required by the elevator car itself on its track and likewise the space required by the counterweight, at least at a reasonable cost and without impairing elevator performance and operational quality. In a traction sheave elevator without machine room, mounting the hoisting machine in the elevator shaft is difficult, especially in a solution with machine above, because the hoisting machine is a sizeable body of considerable weight. Especially in the case of larger loads, speeds and/or hoisting heights, the size and weight of the machine are a problem regarding installation, even so much so that the required machine size and weight have in practice limited the sphere of application of the concept of elevator without machine room or at least retarded the introduction of said concept in larger elevators. If the size of the machine and the traction sheave of the elevator is reduced, then a further problem is often the question of how to ensure a sufficient grip between the hoisting ropes and the traction sheave.
Specification WO 99/43589 discloses an elevator suspended using flat belts in which relatively small diversion diameters on the traction sheave and diverting pulleys are achieved. However, the problem with this solution is the limitations regarding layout solutions, the disposition of components in the elevator shaft and the alignment of diverting pulleys. Also, the alignment of polyurethane-coated belts having a load-bearing steel component inside is problematic e.g. in a situation where the car is tilted. To avoid undesirable vibrations, an elevator so implemented needs to be rather robustly constructed at least as regards the machine and/or the structures supporting it. The massive construction of other parts of the elevator needed to maintain alignment between the traction sheave and diverting pulleys also increases the weight and cost of the elevator. In addition, installing and adjusting such a system is a difficult task requiring great precision. In this case, too, there is the problem of how to ensure sufficient grip between the traction sheave and the hoisting ropes.
On the other hand, to achieve a small rope diversion diameter, rope structures have been used in which the load-bearing part is made of artificial fiber. Such a solution is exotic and the ropes thus achieved are lighter than steel wire ropes, but at least in the case of elevators designed for the commonest hoisting heights, artificial-fiber ropes do not provide any substantial advantage, particularly because they are remarkably expensive as compared with steel wire ropes.